An electric drive can be used as source of driving power in a machine or vehicle, such as, for example, an off-road work machine, a highway truck, or an automobile. An electric drive can supplement the driving power provided by an internal combustion engine or the electric drive can provide all of the driving power for the vehicle. Using an electric drive to supplement or replace the internal combustion engine can reduce the emissions generated during the operation of the vehicle. In addition, the electric drive can increase the fuel efficiency of the vehicle.
An electric drive typically includes a source of electrical power and an electric motor that is connected to one or more ground engaging devices on the vehicle. The source of electrical power, which can be, for example, a battery or an engine, provides the power that is used to operate the electric motor to generate an output torque. The output torque is transferred to the ground engaging devices on the vehicle to propel the vehicle.
Though electric drive technology contributes to improved fuel efficiency, there is no cost effective way to capture the energy while braking and reusing it to drive the machine. The energy can be captured electrochemically in batteries and reused.
U.S. Pat. No. 8,122,991 ('991 patent), titled “Drivetrain, hybrid vehicle, and operating methods therefor,” purports to address improved fuel efficiency for hybrid electric drive vehicles. The '991 patent teaches a drivetrain for a hybrid vehicle with an electrical energy store, which is implemented as a flywheel mass accumulator having a second electric machine. The flywheel mass accumulator is able to be mechanically coupled, via a separate clutch, to an internal combustion engine. The flywheel mass accumulator also is mechanically chargeable and dischargeable. A flywheel mass accumulator provides wear-free energy storage at high energy density in relation to the batteries which are typically used. The losses upon the conversion of mechanical into electrical energy and vice versa are thus dispensed with. The design of the '991 patent, however, does not teach planetary gearing and/or over running clutches to facilitate high-speed energy generation during braking. Accordingly, there is a need for improved fuel efficiency of electric driven machines during braking.